Plastid-encoded RNA polymerase variation in Pelargonium sect Ciconium

Abstract

Cyto-Nuclear Incompatibility (CNI), in which there is a mismatch in the interaction between organelles and nucleus, impacts plant species evolution as it has a direct effect on the fitness of plants. It can reduce fertility and/or result in bleached plants devoid of functional chloroplasts. Understanding the processes leading to CNI could help to improve breeding efforts, especially in cases where species with desirable traits need to be crossed into existing cultivars. To better understand the occurrence of CNI and its effects on plant phenotype, we combined near comprehensive crossing series across a clade of species from Pelargonium section Ciconium with comparative genomics and protein modelling for plastid-encoded RNA polymerase (PEP), as the rpo genes encoding PEP subunits were found to be unusually highly divergent, especially in two length-variable regions. Of all plastome-encoded genes, we found these genes to contain more variation than observed across angiosperms and that this underlies structural variation inferred for PEP in P. sect. Ciconium. This variation, resulting in differing physico-chemical properties of the rpo-encoded peptides, provides a possible explanation for the observed CNI, but we cannot directly correlate plastid related CNI phenotypes to rpo genotypes. This suggests that more than one interaction between the nuclear genome and the plastome genes are needed to fully explain the observed patterns.

Inheritance of Mitochondria in <em>Pelargonium</em> Section <em>Ciconium</em> (Sweet) Interspecific Crosses

“…The list of plant material, DNA extraction protocol, and standard Illumina HiSeq sequencing protocol are the same as those reported in [7]. Additional plant material was collected from herbaria and from living collections (Table 1, copied with permission from [19] and these were subjected to the same treatment with respect to DNA extraction and sequencing. For the sake of convenience, throughout the text four letter acronyms for each accession will be used.…”

“…The resulting hybrids are described in our previous studies [6,7,19], but a short summary is given here for convenience. These studies established a total of 30 different F1 interspecific hybrids and hundreds of plants.…”